[MLB-WIRELESS] RF noise reduction

Jamie Lovick jalovick at doof.org
Wed Feb 19 16:22:15 EST 2003


On Wed, 19 Feb 2003, Matt wrote:
> Just a thought I was having the other day, standard bit here about
> noise increasing over time as more people take up wireless....

This will likely become an issue over time, expecially if every client
uses an Omni, or an antenna with a larger beamwidth than that which is
required to make the link work.

> Instead of trying to get around this by getting a higher gain
> antenna (which then creates noise further away for someone else) if
> I can get a link up with an 8db omni, the link is say East of me, am
> I going to screw up my reception if I surround the north/south/west
> sides of the antenna with something RF absorbing (I'm thinking a
> plastic of some sort). Perhaps this could be used to reduce the
> received as well as transmitted noise and help make an antenna more
> directional without increasing the gain.

If you're just connecting to a local AP, it's best to use a
directional. If you're in a position where you'd be central to others
near by, or have a good all-round line of site, it would be best to use
an Omni, and have others connect with directional antenna. The next node
in the mesh can connect as a client to yours, or via a bridged link, or
as a WDS client.

> I know you'd be covering a smaller area but if it worked then it
> would be possible to put an extra device in and use the same
> frequency (useful for sites with good LOS and multiple links).

When setting up wireless networks, adjoining "cells" should typically be
on a seperate channel. I am not sure if that is the same if it's
connected using WDS.

> I'm wondering if it would screw up the cards (can't really see any
> hassles if its absorbing and not reflecting the signal), or if by
> removing part of the radiation pattern the rest of the pattern would
> get messed up as well.

I wouldn't think so, as you're just adding a substantance to absorb
signal (some plastic pipe that isn't microwave friendly would do), or if
you use something reflective (a metal panel or mesh), you'd be
increasing gain in the given direction opposite the shield (someone who
is better at RF than me can confirm/deny/correct).

> Anyone got tips?

I hope it helps.



Jamie Lovick    <->  IT Consultant    <-> +614 1479 1681
Hobby     : Doof.org                   -> jalovick at doof.org
Director  : Drastic Solutions Pty Ltd  -> jalovick at drasticsolutions.com.au
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